The complete or partial detachment of ligaments, tendons and/or other soft tissues from their associated bones within the body are relatively common injuries. Tissue detachment may occur as the result of an accident such as a fall, overexertion during a work-related activity, during the course of an athletic event, or in any one of many other situations and/or activities. Such injuries are generally the result of excess stress being placed on the tissues.
Partial detachment of a ligament or a tendon, generally referred to “sprain,” usually heals itself if given sufficient time with care to avoid further exposing the injury to undue stress during the healing process. However, when a ligament or tendon is completely detached from its associated bone or bones, or if it is severed as the result of a traumatic injury, partial or permanent disability may result. A number of surgical procedures are thus developed for re-attaching such detached tissues and/or completely replacing severely damaged tissues. In the case where complete replacement is required due to the significant damage to the ligament or tendon, a replacement ligament or tendon graft is needed for such surgical procedures.
Replacement ligament or tendon grafts often involve autografts, for which suitable ligament or tendon graft material is harvested from elsewhere in the patient's body. However, patients often experience considerable pain at the donor site following harvest of the graft material. To avoid additional injury and pain and suffering sustained by the patient, and also to facilitate the recovery process, allografts, such as grafts from a corpse, may be used as replacement ligament or tendon grafts.
In order to be used as an implanting graft, a replacement ligament or tendon graft must meet certain requirements. For example, a replacement ligament or tendon graft typically has a functional cross section diameter greater than 8 mm and a minimum length of about 200 mm. When a graft material does not meet these requirements, it cannot be used and has to be discarded.
It is known in the art to double, triple, or even quadruple the thickness of a tendon graft to produce a replacement graft that has a strength similar to the ligament intended to replace. To do so, a surgeon would usually loop the graft material after it is harvested and suture opposing lengths of the graft material together. See e.g., U.S. Pat. No. 5,298,012 and U.S. Patent Application Publication No. 2007/0250163. Because the folding of the harvested graft material necessarily reduces the length of the resulting replacement graft, only graft materials with sufficient length may be used.
Similarly, to provide a replacement ligament or tendon graft with uniform cross-section thickness, U.S. Pat. No. 7,195,642 discloses folding the two end portions of a harvested tendon graft material, which are thinner than the midsection portion, towards the midsection portion, and suturing them to the adjacent end of the midsection portion to form a double-folded replacement ligament or tendon graft. Such a double-folded ligament or tendon graft may provide a uniform cross-section thickness that would likely meet the functional cross section diameter requirement. However, like the single folding of the graft material described above, because the double folding of the two end portions unavoidably reduces the length of the resulting graft, only graft materials with sufficient length may be used.
Alternatively, a replacement ligament or tendon graft may also be obtained by using a plurality of single tendon strands and placing them together so that at least a portion of one tendon strand is adjacent to a portion of another tendon strand by suture. As such, the replacement ligament or tendon graft thus obtained has at least two regions, one region formed of at least a plurality of tendon strands tied together, and the other region formed of loose segments of the plurality of tendon strands. See e.g., U.S. Patent Application Publication No. 2007/0239275.
In view of the limiting supply of ligament or tendon allograft materials, and because when a graft material does not meet the necessary requirements for implant, it cannot be used and has to be discarded, there still exists a need to provide a means to produce replacement ligament or tendon grafts while making the maximum use of every possible graft material that becomes available.